The use of chest auscultation to diagnose lung conditions, including infections, chronic conditions and other characteristics of the lungs, has been in practice since the invention of the stethoscope in the early 1800s. It is a diagnostic instrument widely used by clinicians to “listen” to lung sounds and flag abnormal patterns that emanate from pathological effects on the lungs. While the stethoscope can be complemented by other clinical tools—including chest radiography and other imaging techniques, or chest percussion and palpation—the stethoscope remains a key diagnosis device due to its low-cost and non-invasive nature. Chest auscultation with standard acoustic stethoscopes is not limited to resource-rich industrialized settings. In low-resource, high-mortality countries with relatively weak health care systems, there is limited access to diagnostic tools like chest radiographs or basic laboratories. As a result, health care providers with variable training and supervision rely upon low-cost clinical tools like standard acoustic stethoscopes to make critical patient management decisions. Indeed, their use is even more pervasive in resource poor areas where low-cost exams are of paramount importance, access to complimentary clinical tools is limited or nonexistent and health care personnel operate with minimal training. Despite its universal adoption, the use of the stethoscope is riddled by a number of issues including subjectivity in interpretation of chest sounds, inter-listener variability and inconsistency, need for advanced medical expertise, and vulnerability to ambient noise that can mask the presence of sound patterns of interest. Thus, while chest auscultation constitutes a portable low cost tool widely used for respiratory disease detection and offers a powerful means of pulmonary examination, it remains riddled with a number of issues that limit its diagnostic capability. Particularly, patient agitation (especially in children), background chatter, and other environmental noises often contaminate the auscultation, hence affecting the clarity of the lung sound itself.
Electronic auscultation combined with computerized lung sound analysis can be used to remedy some of the inconsistency limitations of stethoscopes and provide an objective and standardized interpretation of lung sounds. However, the success of electronic auscultations has been limited to well controlled or quiet clinical settings with adult subjects. The presence of background noise contaminations usually impedes the applicability of these algorithms or leads to unwanted false positives. Contamination of the lung signal picked up by the stethoscope with undesirable noise remains an unaddressed issue, limiting the deployment of computerized auscultation technologies and hampering the usefulness of the stethoscope tool itself, particularly in outpatient clinics or busy health centers where surrounding background noise is an inevitable and hard to control condition. The noise issue is further compounded in pediatric patients where child agitation and crying can add to the distortion of the lung signal picked up by the stethoscope microphone.
Since the invention of the stethoscope, chest auscultations offer a low-cost, highly portable, non-invasive and widely used tools for physical examination of pulmonary health and respiratory disease detection. While they can be complemented with other clinical tools (e.g., chest X-rays), stethoscopes are sometimes the only means of pulmonary examination in low-resource settings such as clinics or health centers in rural or impoverished communities. Such settings usually raise additional challenges for clinical diagnosis pertaining to the examination environment itself. For example, patient agitation (especially in children), background chatter, and other environmental noises can contaminate the sound signal picked up by the stethoscope, hence affecting the clarity of the lung sound itself. Such distortion affects the clarity of the lung sound, hence limiting its clinical value for the health care practitioner. It also impedes the use of electronic auscultation combined with computerized lung sound analysis. However, previous electronic or automated approaches have mainly been validated in well-controlled or quiet clinical settings with adult subjects. In real world settings, the presence of background noise impedes the applicability of pre-existing systems or leads to unwanted false positives. Accordingly, there exists a need to improve the quality of auscultation signals against background contaminations.